This research is intended to provide new information about the control processes that mediate the production and perception of segment durations in adult speech. Emphasis will be placed on the study of syntactic influences on segmental timing in speech production and the way in which the perception of segment durations may play a role in recovering syntactic information. The study of speech production will use a sentence reading paradigm in which key words are inserted in phonetically stable environments. The speech perception experiments will use a category judgement task in which listeners are asked to judge the duration of key words spoken in different sentence contexts. Variations in duration of the key words will be made by deleting or duplicating portions of the waveform electronically. Correlational analyses of the production and perception studies will be conducted to assess the relation between production and perception. In addition, experiments in perceptuo-motor adaptatation will be carried out to further assess the possibility that a single mechanism serves both speech production and perception for the timing of voicing onset in aspirated plosives. The results of these studies will be used to develop a comprehensive model of segmental timing in speech. In addition, rules for the production of segment durations will be implemented as a part of a computer program to synthesize speech from a written phonological transcription.